The element that makes up a large portion of the Earth's solid crust is oxygen.

Here's why:

* Oxygen is the most abundant element in the Earth's crust, making up about 46.6% of its mass. It's primarily found in the form of silicate minerals like quartz and feldspar.

* Silicon comes in second, accounting for around 27.7% of the crust's mass.

* Aluminum is third, making up about 8.1%.

While other elements like iron, calcium, sodium, potassium, and magnesium also play a significant role in the Earth's crust, oxygen and silicon are the dominant components.